Is this normal? New position question

I recently accepted a promotion to unit manager. I was told there would be no pay increase until after the 3 month probationary period. I was just fine with that, because I wrongly assumed I would continue as my present hourly wage. I found out the other day however that I will be instead changed to a salaried employee at my current hourly rate.

The problem is we are severely understaffed right now. I'm working a million hours of overtime, coming in at all hours trying to help cover all the missing shifts. I keep thinking I made a mistake. For 3 months I will be working a million hours a week while taking a pay CUT, since I will not be paid overtime. I'm thinking of approaching my boss, but I don't really know what to ask. Or should I have expected this all along? Having been self employed for so long before working as a nurse so I can't remember the policy at any other job I've had.
I know someone in roughly the same boat. Accepted new salaried managerial position, working a million hours, but not getting weekend differential, night shift differential, or overtime and was given pay rate lower than discussed. The employer is definitely the winner in this situation. All I can say is I hope you can get this to something more acceptable in the future.
So - is it any surprise that "Nurse Manager" positions are so very difficult to fill? Experienced managers are dropping back to staff nurse positions with higher pay and less stress. Organizations are "promoting" experienced staff nurses who are worked to death rather than provided with adequate management development opportunities.... creating more staff dissatisfaction, more turnover, more stress for managers. . . Advice to the OP - make an appointment with your supervisor to discuss this situation and let him/her know that it is untenable. Be prepared to move on if they do not make satisfactory changes - at least upping your salary to compensate for the additional stress. Insist on management training/development and sufficient relief coverage to get your hours down to a manageable level. If they won't accomodate you - move your highly marketable, experienced, "good as gold" self to another organization that will be much more appreciative of your skills and abilities.